Changes in the Vegetation of Sclerophyll Shrubby Woodland Associated With Invasion by Phytophthora cinnamomi

Abstract

Changes in the vegetation of a sclerophyll shrub woodland community growing on deep infertile sands at the northern end of Wilson's Promontory National Park were monitored for infected and control plots over a 5- year period and compared with changes due to disease on a ridge site. In all cases disease appeared as a mosaic of chlorotic and dying plants. The plant community changed to an open sedge woodland characterized by a rediction in tree density, loss of susceptible species, an increase in cover by resistant sedges and increased amount of bare ground. There were highly significant changes in plant density for 12 of the 16 species and in the proportion of these species in the total vegetation. The changes are continuing and there is no evidence as to whether they are irreversible or likely to become part of a cyclic process of disease and recovery. Changes in soil temperature and soil matric water potential were monitored continuously during the 5 years and were correlated with changes in pathogen disease potential, symptom expression and deaths. Disease was most severe not on the plots but on nearby ridge sites with exposed shallow, gravelly soils, and in these plant deaths were more frequent and occurred in more species.